On 11/6/21 7:30 AM, Michael Tope wrote:
You can save raw impedance data to memory on the FA-VA5 while using it
standalone in the field and then download it later to the VNWA
software. The one frustrating limitation of using the unit standalone
is that you are limited to 101 frequency points per memory register
(IIRC, the unit has 10 memory registers). For typical antenna
impedance measurements, that is fine, but for TDR measurements, it can
limit resolution. You can get around this somewhat by saving
sub-segments to different memory registers and then combining them
after download. In theory this would allow you to achieve the
equivalent of saving 1010 frequency points while using the unit
standalone.
I've been fooling with 101 point TDR and a NanoVNA recently - you can
actually get finer resolution with interpolation (zero pad the data
before transforming, is one way). The constraint is that there are
potential ambiguities. And it depends on the SNR. And, if there are
multiple faults, then life gets more complex.
Someone posted a way to determine the position of a short/open with
three measurements. 101 measurements has to be better!
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